1. Field of the Invention
The present invention relates to a method of manufacturing a fuel tank and a fuel tank.
2. Description of Related Art
As a method of attaching an attachment part to a fuel tank formed of a resin, a method has been available in which a portion of a molten resin sheet, of which a fuel tank is formed, is projected by a movable member to form a molten resin projection, the movable member is pulled out of the molten resin projection after this molten resin projection is inserted in an attachment hole that is provided in the attachment part, the molten resin projection is then pressurized by a pressurizing member to expand, and the molten resin is cooled and hardened in a state that a periphery of the attachment hole of the attachment part is held between an expanded portion and the molten resin sheet, so as to fix the fuel tank and the attachment part (for example, U.S. Pat. No. 5,308,427).
In U.S. Pat. No. 5,308,427, after the movable member is pulled out of the molten resin projection, a portion of the molten resin projection, of which the movable member is pulled out, is filled with a core formed of the molten resin, so as to retain a shape of the molten resin projection.
Here, when the movable member moves in a direction to be pulled out of the molten resin projection, the inside of the molten resin projection is brought into a vacuum state. Consequently, the molten resin projection is deformed by following the movement of the movable member and thus turns into an odd shape. Thus, the pressurizing member has to be actuated at a high speed and a high pressure to pressurize and deform the molten resin projection.
However, when the pressurizing member is actuated at the high speed and the high pressure, there is a possibility that a portion of the molten resin that forms the molten resin projection is pushed back to a general section of the molten resin sheet and an amount of the resin required to form an attachment section that is used to attach the attachment part to the fuel tank cannot be secured. Thus, a sufficient amount of the resin needs to be secured by thickening the molten resin sheet, so that the amount of the resin that is required to form the attachment section of the fuel tank can be secured even when the portion of the molten resin is pushed back by pressurization.
In addition, in U.S. Pat. No. 5,308,427, since the molten resin projection is filled with the core, the amount of the resin for the fuel tank tends to increase.